In many cases, a hearing aid with two hearing devices (binaural hearing aid, so called binaural supply) is needed or expedient for the adequate supply of a hearing-impaired patient. Nowadays, digitally programmable hearing systems are used almost exclusively for this, in other words hearing systems, the electroacoustic characteristics of which can and must be externally adjusted (“adapted”) by way of a computer. The main advantage (of digitally) programmable hearing systems lies in the fact that a plurality of electro acoustic parameters can be adjusted, in order to compensate more precisely for the hearing loss. With these hearing devices, the signal processing can take place in an analogue fashion (digitally programmable analogue hearing systems) or in a digital fashion (fully digital hearing systems).
Fully digital hearing devices are hearing systems which convert the analogue microphone signal into a digital signal. The digital signal is then processed according to the commands of the programmed software (algorithm) and the switching circuit integrated on the chip. The digital signals are then converted back into analogue signals and forwarded to the receiver. The incoming signal is measured here at specific time intervals (signal sampling). The more frequent the signal sampling, the better the reproduction of the input signal. The digitalization provides for significantly more complex analyses and filterings in respect of an optimum useful signal/interference noise ratio than was possible with analogue systems.